Project Summary Alzheimer?s disease and related dementias (ADRD) affect >5 million Americans with >15 million family members providing the bulk of ADRD long-term care. Prior ADRD research on informal family caregiving has focused on a single (?primary?) caregiver. Very little is known about the number and type of informal family supports available to people living with ADRD, and in turn the relationship of the use of family resources to adverse health events such as hospitalizations, potentially avoidable hospitalizations (PAH), and formal long- term care support (e.g., nursing home [NH] placement). These events are leading causes of Medicare, Medicaid, and out-of-pocket family expenditures. Understanding the role of informal resources on a person living with ADRD?s health care utilization is imperative and has potential to inform the advancement of interventions to strengthen ADRD care. In a prior analysis using the nationally representative Health and Retirement Study (HRS) linked to Medicare we showed that poorer function of the person with ADRD was associated with more hours of informal caregiving, more inpatient admissions per month, and increased risk of experiencing an out-of-pocket nursing home expenditure. Building on our prior research and in response to PAR-16-161, we propose to evaluate the longitudinal effects of two aspects of informal resources, the number of informal caregivers (spouse, adult children, other family members, and fictive kin) used by persons living with ADRD and the total time of care provided by their informal caregivers, on a person with ADRD?s adverse health events (number/length of hospitalizations, PAH, and NH admissions). To accomplish these objectives, we propose to use HRS linked to Medicare, Medicaid, and the Minimum Data Set (ADRD cases n=2,575). Primary study aims are to: 1) determine how informal caregiving (number of individuals that provide informal care and total time providing care) changes from disease onset up to 12-years post onset and describe how these two factors vary by race/ethnicity (Hypothesis 1: the number of informal caregivers and hours of care provided will increase over the course of ADRD, and non-Whites compared to Whites will have more informal family caregivers and receive more hours of informal care due to having access to more family/fictive kin); and 2) determine how informal caregiving effects adverse health events in persons living with ADRD and determine how this effect differs by race/ethnicity (Hypothesis 2: more informal caregivers and more hours of informal care provision are associated with less ADRD health care utilization. We further hypothesize that non-Whites will receive more informal caregiving than Whites which will result in less formal care compared to Whites). This study has potential to result in important outcomes and will yield new longitudinal nationally representative evidence about the characteristics of informal caregiving resources, going beyond our understanding of only a primary caregiver and the link of caregiving resources to health care utilization.